Power supply apparatus, backlight assembly and liquid crystal display apparatus having the same

ABSTRACT

A power supply apparatus includes an inverter controller, a power transforming part and a connecting part. The power transforming part converts a direct current supplied from the inverter controller into an alternating current to output first and second polarity currents. The connecting part outputs the first and second polarity currents to first and second end portions of a load through first and second terminals, respectively and has a third terminal to receive a sensed signal in response to the first or second polarity currents so as to output the sensed signal. The first terminal is spaced apart from the second terminal by a first insulating distance, and the third terminal is spaced apart from the first or second terminals adjacent to the third terminal by a second insulating distance. Therefore, the sensed signal is independent of the output power, thereby increasing the sensing efficiency.

TECHNICAL FIELD

The present invention relates to a power supply apparatus, a backlightassembly and a liquid crystal display (hereinafter, referred to as LCD)apparatus having the same, and more particularly to a power supplyapparatus capable of improving sensing efficiency of an output power, abacklight assembly and an LCD apparatus having the same.

BACKGROUND ART

An LCD apparatus, generally, is a light receiving type display apparatusthat displays an image using the light that is provided from anexterior. Therefore, the LCD apparatus needs a backlight assembly thatprovides the LCD apparatus with the light. The LCD apparatus is disposedon a rear of the backlight assembly.

The backlight assembly has various characteristics, for example, such ashigh luminance, high efficiency, uniform luminance, long lifetime, thinthickness, light weight and low cost and so on. For example, a backlightassembly applied to an LCD apparatus for a notebook computer requires alamp having a long lifetime and low power consumption. A backlightassembly applied to an LCD apparatus for a monitor or a televisionreceiver requires a lamp having high luminance.

Especially, the backlight assembly applied to the LCD apparatus for thetelevision requires a lamp having higher luminance and longer lifetimethan those of the backlight assembly applied to the LCD apparatus forthe monitor or the notebook computer. For a display apparatus such asthe television receiver, an external electrode fluorescent lamp (EEFL)has been developed because a conventional cold cathode fluorescent lamp(CCFL) may not satisfy specific conditions required for the LCDapparatus for the television receiver. The lamp for the LCD apparatusfor the television receiver may be divided into the EEFL having externalelectrodes outwardly located at both ends thereof and anexternal/internal electrode fluorescent lamp (EIFL) having one externalelectrode outwardly located at a first end portion and one internalelectrode inwardly located at a second end portion opposite to the firstend portion.

For those purposes, an inverter that may drive a plurality of lamps inparallel has been developed. When driving the lamps in parallel, aseparate feedback unit is necessary to the lamps so as to prevent fireof the lamp and deterioration of display quality.

As aforementioned, a power supply apparatus having high quality isnecessary to the lamps of the LCD apparatus.

DISCLOSURE OF THE INVENTION

The present invention provides a power supply apparatus capable ofimproving sensing efficiency of an output power having high quality.

The present invention also provides a backlight assembly having theabove power supply apparatus.

The present invention also provides an LCD apparatus having the abovepower supply apparatus.

The power supply apparatus in accordance with one exemplary embodimentof the present invention includes an inverter controller, a powertransforming part and a connecting part The inverter controller outputsa direct current that is provided from an exterior in response to apredetermined control signal. The power converter converts the directcurrent into an alternating current, and transforms voltage of thealternating current to output first and second polarity currents. Theconnecting part outputs the first polarity current into a first endportion of a load through a first terminal and outputs the secondpolarity current into a second end portion of the load through a secondterminal. The connecting part also receives a sensed signal inaccordance with the first or second polarity current through a thirdterminal to output the signal. The first terminal is spaced apart fromthe second terminal by a first insulating distance, and the thirdterminal is spaced apart from the first or second terminal adjacent tothe third terminal by a second insulating distance.

The backlight assembly in accordance with one exemplary embodiment ofthe present invention includes a lamp driving part, a light emittingpart, an inverter controller, a power transforming part and a connectingpart. The lamp driving part converts a direct current that is providedfrom an exterior into an alternating current, and transforms voltage ofthe alternating current to output the alternating current The lightemitting part includes a lamp having at least one end portion, to whichhigh voltage alternating current is applied in response to thealternating current, thereby generating a light. The inverter controllerhas a light controlling part, which increases luminance of the light,and responds to a predetermined control signal to output a directcurrent that is provided from an exterior to the inverter controller.The power transforming part converts the direct current into analternating current, and transforms voltage of the alternating currentto output first and second polarity currents. The connecting partoutputs the first polarity current into a first end portion of a lampthrough a first terminal, and outputs the second polarity current into asecond end portion of the lamp through a second terminal. The connectingpart also receives a sensed signal in accordance with the first andsecond polarity currents through a third terminal to output the signal.The first terminal is spaced apart from the second terminal by a firstinsulating distance, and the third terminal is spaced apart from thefirst or second terminal adjacent to the third terminal by a secondinsulating distance.

The LCD apparatus in accordance with one exemplary embodiment of thepresent invention includes a backlight assembly, an inverter controller,a power transforming part and a connecting part.

The backlight assembly includes a lamp driving part, a light emittingpart and a light controller. The lamp driving part converts theexternally provided direct current into an alternating current, andtransforms a voltage of the alternating current to output thealternating current. The light emitting part includes a lamp unit havinga plurality of lamps connected in parallel so as to emit a light bymeans of the transformed alternating current. The light controllerincreases the luminance of the light from the light emitting part.

The inverter controller disposed on the light controller includes adisplay unit, and the inverter controller outputs an externally provideddirect current to the power transforming part in response to apredetermined control signal. The display unit receives the light fromthe light emitting part through the light controller to display animage.

The power transforming part converts the direct current into analternating current, and transforms a voltage of the alternating currentto output first and second polarity currents.

The connecting part provides the first and second polarity currents toend portions of the lamp through first and second terminals,respectively. The connecting part outputs the sensed signal inaccordance with the first or second polarity current through a thirdterminal. The first terminal is spaced apart from the second terminal bya first insulating distance. The third terminal is spaced apart from thefirst or second terminal adjacent thereto by a second insulatingdistance.

Therefore, the terminals that receives the signal of power supply levelsupplied from the power supply apparatus is integrally formed with thepower supply apparatus, and a distance between the end portions of thetransformer and a distance between the end portion of the transformerand the terminal are greater than a distance necessary to insulate,thereby increasing sensing efficiency in accordance with the powersupply level.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present invention will becomereadily apparent by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a block diagram showing a power supply apparatus according toan exemplary embodiment of the present invention;

FIG. 2 is a perspective view showing the power supply apparatus shown inFIG. 1;

FIG. 3 is a schematic circuit diagram showing the power supply apparatusshown in FIG. 1;

FIG. 4 is a schematic circuit diagram showing a detecting signalgenerating part shown in FIG. 3;

FIG. 5 is a schematic circuit diagram showing a lamp driving part of abacklight assembly according to an exemplary embodiment of the presentinvention; and

FIG. 6 is an exploded perspective view showing an LCD apparatusaccording to an exemplary embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram showing a power supply apparatus according toan exemplary embodiment of the present invention, and FIG. 2 is aperspective view showing the power supply apparatus shown in FIG. 1. Inthis exemplary embodiment, a power supply apparatus mounted on a printedcircuit board (PCB) will be described.

Referring to FIGS. 1 and 2, a power supply apparatus 100 includes aninverter controller 110, a power transforming part 120, a connectingpart 130 and a detecting signal generating part 140. The power supplyapparatus 100 supplies an externally provided power to a load part thatis a lamp 200. The power supply apparatus 100 receives a feedback of thepower supplied to the lamp 200 and sensed by a power sensor 300. Thepower supply apparatus 100 lowers a voltage level of the power suppliedto the lamp when the sensed power is higher than a predetermined level,and raises the voltage level of the power supplied to the lamp when thesensed power is lower than the predetermined level.

Preferably, the power supply apparatus 100 is mounted on one PCB, sothat a first terminal 132 outputting an alternating current suppliedfrom the power transforming part 120 is spaced apart from a secondterminal 134 by a predetermined distance d1, and a third terminal 136 isspaced apart from the first or second terminals 132 and 134 by apredetermined distance d2. The third terminal 136 receives a feedbacksignal from the power sensor 300 sensing an output power applied to thelamp 200. Thus, the first, second and third terminals 132, 134 and 136are formed on a PCB, thereby increasing a sensing efficiency.

The inverter controller 110 provides the power transforming part 120with a direct current (VIN) that is provided from an exterior, inresponse to a control signal 141 provided from a detecting signalgenerating part 140.

The power transforming part 120 converts the direct current (VIN) outputfrom the inverter controller 110 into an alternating current, andtransforms voltage of the alternating current so as to output thealternating current to the lamp 200 through the first and secondterminals 132 and 134.

Referring to FIG. 2, the connecting part 130 includes first and secondconnecting parts 130 a and 130 b. The first connecting part 130 a isintegrally formed with the power supply apparatus 100. The secondconnecting part 130 b is connected to a power supplying line connectedto a hot electrical terminal of the lamp 200 and a power supplying lineconnected to a cold electrical terminal of the lamp 200 connected toeach other in parallel. When the first connecting part 130 a has asocket type, the second connecting part 130 b has a plug type. The firstconnecting part 130 a includes a first socket 132 a connected to a firstend portion of the power transforming part 120, a second socket 134 aconnected to a second end portion of the power transforming part 120,and a third socket 136 a connected to the detecting signal generatingpart 140. The second connecting part 130 b includes a first plug 132 binserted into the first socket 132 a, a second plug 134 b inserted intothe second socket 134 a, and a third plug 136 b connected to the powersensor 300. The first terminal 132 includes the first socket 132 acoupled to the first plug 132 b, the second terminal 134 includes thesecond socket 134 a coupled to the second plug 134 b, and the thirdterminal 136 includes the third 136 a coupled to the third plug 136 b.

Preferably, the first terminal 132 is spaced apart from the secondterminal 134 by a first insulating distance d1 determined by a safetystandard, and the second terminal 134 is spaced apart from the thirdterminal 136 by a second insulating distance d2 determined by the safetystandard. The insulating distance may be a distance between outersurfaces of the sockets. The insulating distance may also be a distancebetween a wiring disposed between the first socket 132 a and the powertransforming part 120 and another wiring disposed between the secondsocket 134 a and the power transforming part 120. The insulatingdistance may also be a distance between the wiring disposed between thesecond socket 134 a and the power transforming part 120 and anotherwiring disposed between the third socket 136 a and the detecting signalgenerating part 140.

When an UL1950 is adopted as the safety standard and the alternatingcurrent supplied from the power transforming part 120 is 1 kV, the firstinsulating distance d1 is no less than about 2.1 mm.

For example, when a voltage required from a conventional EEFL is about±750 volts, a potential difference between the first and second ends ofa voltage of an alternating current output from the power transformingpart 120 is about 1,500 volts. That is, when a level of an alternatingcurrent supplied from the power transforming part 120 is no less than1,000V, the first insulating distance d1 is no less than about 3 mm andthe second insulating distance d2 is no less than about 2 mm.

The power sensor 300 sensing variations of the alternating current isdisposed adjacent to the power supplying line connected to an endportion of the lamp 200. The power sensor 300 senses variations of thealternating current, and provides the sensed signal 131 to a detectingsignal generating part 140 through the third terminal 136.

In order to provide a constant current to the lamp 200, the detectingsignal generating part 140 receives the signal 131 from the power sensor300 through the third terminal 136, which indicates the variation of thealternating current output from the power transforming part 120. Thedetecting signal generating part 140 compares the signal 131 with apredetermined reference signal to generate a detecting signal 141, andprovides the generated signal 141 to the inverter controller 110 as acontrol signal.

The first, second and third terminals 132, 134 and 136 of the powertransforming part 120 are integrally formed with the power supplyapparatus 100, thereby increasing the sensing efficiency. The powertransforming part 120 of the power supply apparatus 100 generates firstand second polarity currents. The third terminal 136 receives the sensedsignal 131 generated from the power sensor 300, which senses the powerapplied to the lamp 200. That is, the first, second and third terminals132, 134 and 136 are integrally formed with an inverter PCB. In thisexemplary embodiment, the first insulating distance d1 is no less thanabout 3 mm such that the first and second terminals 132 and 134 areinsulated from each other. Also, the second insulating distance d2 is noless than about 2 mm such that the third terminal 136 may be insulatedfrom the first or second terminals 132 and 134.

FIG. 3 is a schematic circuit diagram showing the power supply apparatusshown in FIG. 1. In FIG. 3, a lamp driving apparatus will be describedas the power supply apparatus.

Referring to FIGS. 1 to 3, the lamp driving apparatus includes aswitching part 112 having a first switch SW1, the inverter controller110 having a diode D1, an inverting part 114 and a controlling part 110,the power transforming part 120 having a transformer, the connectingpart 130 and the detecting signal generating part 140. The lamp drivingapparatus converts the externally provided direct current into thealternating current, and transforms the voltage of the alternatingcurrent so as to provide the transformed alternating current to the lamp200. The lamp driving apparatus controls the voltage level of thealternating current that is provided to the lamp 200 in response to thesensed signal 131 generated from the power sensor 300. The invertingpart 114 includes an inductor L, a capacitor C1, a second switch SW2, athird switch SW3 and a switching controlling part 114 a.

The switching part 112 having the first switch SW1 is connected betweenthe power supply (now shown) and the inductor L. The inductor L isconnected to a middle tab of the transformer. Therefore, the inductor Lcontrols the direct current (VIN) supplied from an external power supplyin response to a switching control of the controlling part 116 togenerate the direct current to the inverting part 114 as a pulse shape.The direct current has a voltage level from about 3V to about 30V. Thefirst switch SW1 may include an analogue switch, a bipolar junctiontransistor (BJT), a field effect transistor (FET), etc.

A first terminal is disposed between the first switch SW1 and theinductor L. The diode D1 is connected between the first terminal and asecond terminal that is grounded. A cathode of the diode D1 is connectedto an output terminal of the switching part 112, and an anode of thediode D1 is grounded so as to prevent a rush current generated by theinverting part 114 from being supplied to the switching part 112. Thecapacitor C1 is connected to the power transforming part 120 inparallel. A first terminal of the capacitor C1 is connected to a firstterminal of the second switch SW2, and a second terminal of thecapacitor C1 is connected to a first terminal of the third switch SW3.Second terminals of the second and third switches SW2 and SW3 areconnected to the ground.

The power sensor 300 senses the level of the alternating currentprovided to the lamp 200, and supplies the sensed signal 131 to thedetecting signal generating part 140 through the third terminal 136 ofthe connecting part 130. The power sensor 300 also senses variations ofcurrent and resistance at the output terminal of the transformer. Thelamp 200 may include a cold cathode fluorescent lamp (CCFL), an EEFL oran external and internal electrode fluorescent lamp (EIFL). The lamp 200may include a plurality of the CCFLs, a plurality of the EEFLs or aplurality of the EIFLs.

When the power sensor 300 senses the variation of the voltage, and thepower sensor 300 sensing an output voltage is disposed adjacent to asecond windings of the transformer, an electric field is generatedbetween the sensor and the second windings so that an induced currentflows in the power sensor 300. Therefore, the power sensor 300 sensesthe variation of the voltage. The power sensor 300 adjacent to thesecond windings of the transformer may include a noise barrier shieldingan electrical noise that is provided from an exterior to the transformeror an electromagnetic interference (EMI) shield.

When a plurality of the lamps is used, a plurality of the power sensors300 is disposed corresponding to an end portion of each of the lamps,thereby sensing the variation of the voltage. The lamp driving apparatusincludes a detecting signal generating part 140. The lamp drivingapparatus may include a plurality of the detecting signal generatingparts 140.

When the power sensor 300 senses the variation of the current, the powersensor 300 may include a photo diode. Because a voltage signal is easierto control than a current signal, the power sensor 300 converts thecurrent signal to the voltage signal by a resistor having smallresistance or a feedback of an amplifier.

The detecting signal generating part 140 compares the voltage levelsensed by the power sensor 300 with a predetermined voltage level togenerate the detecting signal 141. The detecting signal generating part140 provides the detecting signal 141 to the controlling part 116 sothat the power supply apparatus provides constant current to the lamp200 by means of the controlling part 116.

The controlling part 116 is connected to the first switch SW1 togenerate a switching signal 117 controlling the constant current of thelamp 200 in response to an on/off signal (not shown) and a dimmingsignal (not shown) that is provided from an exterior to the controllingpart 116.

When the first switch SW1 is closed (turned on), the direct current issupplied to the inverting part 114 so that the alternating current issupplied to the load or the lamp. The alternating current may be in asine wave form. Current flows from a power supply (+V) into the middletab of the transformer 120 through the inductor L. The switchcontrolling part 114 a controls the second switch SW2 and the thirdswitch SW3 in response to an on/off signal. The second and thirdswitches SW2 and SW3 are alternately turned on and turned off togenerate an alternating current wave in the second wiring of thetransformer 120. Control frequency of the second and third switches SW2and SW3 may be constant. Preferably, the control frequencies of thesecond and third switches SW2 and SW3 are synchronized with a resonantfrequency of a reactive part, which is the transformer, of the circuit.

When the second and third switches SW2 and SW3 are synchronized with theresonant frequency of the reactive part of the circuit, the controllingpart 116 generates the sine wave. The predetermined operationfrequencies of the second and third switches SW2 and SW3 are from about10 kHz to about 100 kHz. A voltage of the first windings of the powertransforming part 120, that is the transformer, is amplified inaccordance with a voltage of the second windings of the powertransforming part 120 and the windings of the transformer. The voltageof the second windings is greater than a striking voltage of the lamp200.

The striking voltage of the lamp 200 is independent of length, diameterand packing pressure of the lamp 200, but the striking voltage of thelamp 200 depends on a plurality of lamp parameters except the length,the diameter and the packing pressure of the lamp 200. When the voltageof the second windings of the transformer 120 is greater than thestriking voltage, current flows through the lamp 200 to turn on thelamp. The current flowing the lamp 200 may be controlled by means of aballast inductor (not shown).

When the first switch SW1 is turned off, the alternating current is notsupplied to the inverter circuit. However, current charged in theinductor has been supplied from the power supply (+V) to the middle tabof the transformer 120 through the inductor L and the diode D1 until thecharged energy is completely exhausted. The first switch SW1 controlsthe direct current in accordance with the output of the controlling part116 to control the alternating current supplied to the lamp 200, therebycontrolling the luminance of the lamp in accordance with the input froma liquid crystal display LCD apparatus (not shown).

A sensor is disposed adjacent to the output windings of the transformerconnected to the end portions of the lamp so as to sense whether or notthe constant current is supplied to the lamp through the sensed voltageby the antenna. The sensor may include an antenna.

When the lamp is shut down, the antenna adjacent to the output windingsof the transformer does not sense any voltage while the invertersupplies the alternating current to the lamp through the input windings,thereby the output windings of the transformer having no load.Therefore, the current may not be supplied to the lamp.

When the voltage sensed by means of the antenna adjacent to the outputwindings of the transformer is no more than a predetermined criticalvoltage, one of the lamps is shut down. Therefore, an alternatingcurrent having decreased voltage may be supplied to the inverting partby means of the switch.

The voltage for the initial driving of the lamp is higher than thevoltage for the normal driving of the lamp so that an alternatingcurrent having higher voltage is supplied to the lamp in an initialdriving, and an alternating current having lower voltage is supplied tothe lamp in a normal driving, thereby reducing power consumption.

FIG. 4 is a schematic diagram showing a detecting signal generating partshown in FIG. 3.

Referring to FIGS. 3 and 4, the detecting signal generating part 140includes a second diode D2, a second capacitor C3, a first resistor R1,a second resistor R2 and a comparator 142.

A level of a signal 131 sensed by the power sensor 300 connected to thesecond windings of the transformer 120 is decreased by the second diodeD2, the second capacitor C2 connected to the second diode D2, the firstresistor R1 and the second resistor R2. The signal 131 having thedecreased level is supplied to a first input end portion (+) of thecomparator 142 so that the signal 131 is compared with a predeterminedsignal supplied to a second input end portion (−) to generate thedetecting signal 141. The generated detecting signal 141 is thensupplied to the controlling part 116.

The controlling part 116 having the detecting signal 141 controls on/offof the first switch SW1 controlling the direct current that is providedfrom an exterior to the controlling part 116.

FIG. 5 is a schematic diagram showing a lamp driving part of a backlightassembly according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the lamp driving apparatus of the backlightassembly includes the inverter controller 110, the power transformingpart 120, the power sensor 300 and the detecting signal generating part140. The inverter controller 110 has a power transistor Q1, the diodeD1, the inverting part 114 and the controlling part 116. The powertransforming part 120 has the transformer. The power sensor 300 isdisposed adjacent to the output end portion of the transformer. The lampdriving apparatus converts the externally provided direct current intothe alternating current, thereby supplying the alternating current to alamp array. The lamp array has a plurality of EEFLs connected to eachother in parallel.

The lamp array may also include a plurality of external and internalelectrode fluorescent lamps (EIFLs). The ballast capacitor may beconnected to one end portion or two end portions of the lamps.

The power transistor Q1 is turned on in response to a switching signal117 output from the controlling part 116 through a gate to control thedirect current output from a source thereof into the inverting part 114through a drain thereof.

A cathode of the diode D1 is connected to the drain of the powertransistor Q1, and an anode of the diode D1 is grounded to prevent arush current of the inverting part 114 from being supplied to the powertransistor Q1.

The inverting part 114 includes the inductor L, a resonant capacitor C1,a third resistor R3, a fourth resistor R4, a second transistor Q2 and athird transistor Q3. An end portion of the inverting part 114 isconnected to the drain of the power transistor Q1 to transform anintermittent direct current supplied from the power transistor Q1 to afirst alternating current. The inverting part 114 transforms voltage ofthe first alternating current to generate a second alternating current,thereby supplying the second alternating current to the powertransforming part 120. The inverter includes a resonant Royer invertercircuit.

In particular, a first end portion of the inductor L is connected to thedrain of the power transistor Q1 to remove impulse signal from thedirect current, thereby outputting the direct current without theimpulse signal through a second end portion of the inductor L. When thepower transistor Q1 is turned on, the inductor L charges energy. Whenthe power transistor Q1 is turned off, the inductor L supplies counterelectromotive force to the diode. Therefore, the inductor L stabilizescurrent as a switching regulator.

The transformer of the power transforming part 120 includes the firstwindings having a first winding T1 and a second winding T2 and thesecond windings having a third winding T3. The transformer outputs thealternating current provided to the first winding T1 through theinductor L of the inverting part 114 to the third winding T3 of thesecond windings by means of electromagnetic induction, therebygenerating a high voltage. The high voltage is supplied to a lamp array.The direct current is supplied from the inductor L to the first windingT1 through the middle tab.

The second winding T2 turns on one of the second transistor Q2 and thethird transistor Q3 in accordance with the alternating current providedto the first winding T1.

The resonant capacitor C1 is connected to end portions of the firstwinding T1 of the transformer to form an LC resonant circuit with theinductance signal of the first winding T1. The second winding T2connected to the input end portion of the transformer turns on one ofthe second transistor Q2 and the third transistor Q3.

A direct current is applied to a base of the second transistor Q2through the third resistor R3, and a collector of the second transistorQ2 is connected to a first end portion of the resonant capacitor C1 andthe first winding T1 in parallel to control the power transforming part120. The direct current is applied to a base of the third transistor Q3through the fourth resistor R4, and a collector of the third transistorQ3 is connected to a second end portion of the resonant capacitor C1 andthe first winding T1 in parallel to control the power transforming part120. Emitters of the second and third transistors Q2 and Q3 aregrounded.

The power sensor 300 includes an antenna 310 spaced apart from theoutput end portion of the transformer 120 by a minimum insulatingdistance. The output end portion of the transformer is a wire throughwhich the alternating current from the third winding T3 is supplied tothe lamp. The minimum insulating distance is the second insulatingdistance. The power sensor 300 senses the voltage of the wire to providethe sensed signal to the detecting signal generating part 140. When theantenna 310 is disposed adjacent to the second windings of thetransformer, electric field is formed between the antenna 310 and thewire connected to the output portion of the second wirings, therebysensing the voltage.

When a coil antenna 310 is disposed adjacent to the second windings,another transformer having the second windings and the coil antennagenerates a current in accordance with the induced voltage. The currentis supplied to the detecting signal generating part 140 to serve as aninverter feedback.

The controlling part 116 includes a pulse width modulation (PWM)controlling part 116 a and a metal oxide semiconductor field effecttransistor (MOSFET) driving part 116 b that is a switch driving part.The controlling part 116 is controlled by means of an on/off signal inresponse to the dimming signal that is provided from an exterior to thecontrolling part 116 and the detecting signal provided from thedetecting signal generating part 140 to supply the switching signal 117to the power transistor Q1. The switching signal 117 is used to controlthe level of the alternating current. The dimming signal controls theluminance of the lamp, and the dimming signal is a digital signal havinga predetermined duty. The dimming signal may be generated by a manualinput. The signal sensed from the output end portion of the transformer120 supplying the current having increased voltage to the lamp 200 iscompared with a predetermined standard signal to form the detectingsignal.

The MOSFET driving part 116 b amplifies the signal used to control thelevel of the alternating current provided from the PWM controlling part116 a, and the MOSFET driving part 116 b supplied the signal to thepower transistor Q1. The MOSFET driving part 116 b is used to amplify asignal having a low level because the signal output from the PWMcontrolling part 116 a generally has a low level and a signal having ahigher level is necessary to the power transistor Q1.

Hereinafter, a power output part, that is the inverting part 114 and thepower transforming part 120, converting an alternating current havinglow level to an alternating current having high level will be explained.

The direct current transformed by the power transistor Q1 is applied tothe base of the second transistor Q2 through the resistor seriallyconnected to the base of the second transistor Q2. The base of thesecond transistor Q2 is coupled to the input end portion of theinverting part 114. The first winding T1 having the middle tab of thetransformer 120 is connected in parallel between the collectors of thesecond and third transistors Q2 and Q3. Emitters of the second and thirdtransistors Q2 and Q3 are grounded. The capacitor C1 is also connectedin parallel to the first winding T1.

The direct current is supplied to the middle tab of the first winding T1of the transformer 120 through the inductor L having a choke coil. Thechoke coil transforms the current supplied from the inverting part 114to the constant current.

The number of windings of the third winding T3 of the transformer 120 islarger than that of the first winding T1, thereby increasing the voltagesupplied to the first winding T1. A plurality of lamps of the lamp arrayis connected in parallel with the third winding T3 of the transformer120 to supply the constant voltage to each of the fluorescent lamps. Theincreased alternating current having the constant voltage may have apositive level and a negative level substantially equal to the positivelevel. The increased alternating current having the constant voltage mayalso have a constant interval between a minimum level and a maximumlevel.

A first end portion of the second winding T2 of the transformer of thepower transforming part 120 is connected to the base of the secondtransistor Q2, and a second end portion of the second winding T2 of thetransformer of the power transforming part 120 is connected to the baseof the third transistor Q3. The power transforming part 120 provides thevoltage supplied from the second winding T2 to the bases of the secondand third transistors Q2 and Q3.

The power sensor 300 includes one antenna 310. The power sensor 300 mayinclude a plurality of the antennas connected to the EEFLs. The powersensor 300 is connected to the second windings of the transformer. Thelamp driving apparatus may include a plurality of the detecting signalgenerating parts 140, and the number of the detecting signal generatingparts 140 may be equal to the number of the antennas.

Hereinafter, an operation of the inverter transforming the directcurrent to the alternating current will be explained.

Firstly, when the transformed direct current is supplied to theinverter, the current is supplied to the first winding T1 of thetransformer 120 through the inductor L, the pulse current is supplied tothe base of the second transistor Q2 through the first resistor R3, thepulse current is supplied to the base of the third transistor Q3 throughthe second resistor R4. The resonant capacitor C1 resonates in thereactance of the first windings of the transformer of the powertransforming part 120. The first windings include the first winding T1.Therefore, the increased voltage is generated between the third windingT3. The voltage is increased in accordance with a turn ratio of thefirst winding T1 to the third winding T3 of the transformer. A directionof the current of the second winding T2 of the first windings is anopposite direction to the current of the first winding T1.

The voltage is increased in accordance with the turn ratio to generate ahigh voltage wave, thereby preventing the flickering of the lamp array.The end portions of the third winding T3 of the transformer resonate inaccordance with a frequency and a phase of the high voltage wave.

The power supply apparatus includes a plurality of the EEFLs connectedin parallel. The power supply apparatus may include a plurality of theEIFLs. The power supply apparatus may also include a plurality of theEEFLs and EIFLs. When the EIFLs are connected in parallel, the invertermay include the external electrodes connected to each other and theinternal electrodes connected to each other. However, the externalelectrodes may be connected to the internal electrodes.

When the EEFLs or the EIFLs are connected in parallel, the alternatingcurrent having the current voltage is supplied to two end portions ofthe fluorescent lamps in response to the dimming signal that is providedfrom an exterior to the lamps, thereby controlling the luminance of thefluorescent lamps.

When one of the fluorescent lamps connected in parallel is shut down,the load exhausting the power decreases. The decreased power consumptionis sensed by means of the antenna connected to the second windings ofthe transformer so that the direct current is controlled by means of thefeedback of the sensed power consumption. Therefore, the constantcurrent is supplied to the lamps. When at least one fluorescent lampoperates normally, a closed loop is formed so that current on a tubeflows through the closed loop, thereby preventing a fire.

The backlight assembly senses the power generated from the secondwindings of the transformer. Hereinafter, an LCD apparatus having thebacklight assembly is explained.

FIG. 6 is an exploded perspective view showing an LCD apparatusaccording to an exemplary embodiment of the present invention. The LCDapparatus has a light source disposed on a side thereof.

The LCD apparatus 900 includes an LCD module 700, a front cover 810receiving the LCD module 700 and a rear cover 820. An image signal issupplied to the LCD module 700 so that the image is displayed. The LCDmodule 700 includes a display unit 710 having an LCD panel 712displaying the image.

The display unit 710 includes the LCD panel 712, a data PCB 714, a gatePCB 719, a data tape carrier package TCP 716 and a gate TCP 718. The LCDpanel 712 includes the thin film transistor TFT substrate 712 a, a colorfilter substrate 712 b and a liquid crystal layer (not shown), therebydisplaying the image.

In particular, the TFT substrate 712 a is a transparent glass substratehaving a plurality of TFTs arranged in a matrix shape on the transparentglass substrate. Data lines are connected to source electrodes of theTFTs, and gate lines are connected to gate electrodes of the TFTs. Aplurality of pixel electrodes having a transparent conductive materialsuch as indium tin oxide ITO, indium zinc oxide IZO, etc. is connectedto the drain electrodes.

When electrical signals are supplied to the date lines and the gatelines, the electrical signals are supplied to the source electrode andthe gate electrode of each of the TFTs. The TFTs are turned on/off inresponse to the electrical signal to supply electrical signal necessaryto form a pixel to the drain electrode.

The color filter substrate 712 b is corresponding to the TFT substrate712 a. The color filter substrate 712 b includes a red color filter, agreen color filter and a blue color filter. The color filters are formedthrough depositing and patterning thin films. When a light passesthrough the color filter substrate 712 b, a predetermined color isdisplayed by the color filters. A common electrode having ITO is formedover the color filter substrate 712 b.

When the power is supplied to the gate electrode and the sourceelectrode of each of the transistors of the TFT substrate 712 a, anelectric field is formed between the pixel electrodes of the TFTsubstrate 712 a and the common electrode of the color filter substrate.The arrangement of the liquid crystal disposed between the TFT substrate712 a and the color filter substrate 714 b is varied in response to anelectric field applied thereto, and thus a light transmittance thereofis changed, thereby displaying the image.

In order to control a time when the liquid crystal varies thearrangement, a driving signal and a timing signal are supplied to thegate line and the data line of the TFT, respectively. The data TCP 716disposed on a data portion of the LCD panel 712 controls a time when thedata driving signal is supplied. The gate TCP 718 disposed on a gateportion of the LCD panel 712 controls a time when the gate drivingsignal is supplied. The data TCP 716 and the gate TCP 718 are flexiblecircuit boards.

The data PCB 714 and the gate PCB 719 are connected to the data TCP 716in the data portion and the gate TCP 718 in the gate portion,respectively. The image signal is externally provided to the LCD panel712 so that the data PCB 716 and the gate PCB 719 supply the drivingsignal to the gate line and the data line.

The data PCB 714 and the gate PCB 719 include the source portion and thegate portion, respectively. The source portion is formed on the data PCB714, and the source portion supplies an image signal to the LCD panel712. The image signal is supplied from an external informationprocessing apparatus (not shown) such as a computer. The gate portionsupplies the gate driving signal to the gate line of the LCD panel 712.

The data PCB 714 and the gate PCBs 719 generate driving signals of theLCD apparatus such as the gate driving signal, the data signal, thetiming signals, etc. Therefore, the data PCB 714 and the gate PCB 719output the gate and data driving signals to the gate and data lines ofthe LCD panel 712 through the gate and data TCPs 718 and 716,respectively. The gate driving signal and the data signal are suppliedin a predetermined time by means of the timing signals.

A backlight assembly 720 supplying a uniform light to the display unit710 is disposed under the display unit 710. The backlight assembly 720includes first and second lamp units 723 and 724 disposed on two sidesof an LCD module 700 to generate light. The first lamp unit 723 includesfirst and second lamps 723 a and 723 b, and the first lamp unit 723 iscovered by a first lamp cover 722 a. The second lamp unit 725 includesthird and fourth lamps 725 a and 725 b, and the second lamp unit 725 iscovered by a second lamp cover 722 b. The LCD apparatus includes thepower supply apparatus supplying power to the first to fourth lamps 723a, 723 b, 725 a and 725 b.

A light guide plate 724 has a size corresponding to the LCD panel of thedisplay unit 710. The light guide plate 724 is disposed under the LCDpanel 712 to change direction of the light generated by the first andsecond lamp units 723 and 725, thereby guiding the light into thedisplay unit 710.

The light guide plate 724 has a hexahedron shape having a uniformthickness. The light guide plate 724 may have a wedge shape. The firstand second lamp units 723 and 725 are disposed on the sides of the lightguide plate 724 facing each other to increase light efficiency. Thefirst and second lamp units 723 and 725 may have a plurality of lamps.

The light that exits from the light guide plate 724 passes through theoptical sheets 726 disposed on the light guide plate 724 to generate alight having uniform luminance. A reflecting plate 728 disposed underthe light guide plate 724 reflects a leaked light from the reflectingplate 728 into the light guide plate 724 to increase the lightefficiency.

A mold frame 730, which is a receiving case, secures the display unit710 and the backlight assembly 720. The mold frame 730 has a rectangularparallelepiped shape, and the upper face of the mold frame 730 isopened.

The data PCB 714 and the gate PCB 719 of the display unit 710 are foldedoutwardly, and secured on the undersurface of the mold frame 730 to forma chassis 740. The chassis 740 prevents the display unit 710 from beingseparated therefrom. A portion of the chassis 740 is open to expose theLCD panel 710. Sidewalls of the chassis 740 are folded inwardly andvertically to secure the LCD panel 710 with the LCD apparatus.

The LCD apparatus includes the light guide plate and a plurality oflamps disposed on the sidewalls of the light guide plate. The LCDapparatus may have a direct illuminating light source.

INDUSTRIAL APPLICABILITY

As mentioned above, end portions of a transformer of a power supplyapparatus are spaced apart from each other by an insulating distance,and a terminal receiving a signal from a sensor sensing a powergenerated by the power supply apparatus is integrally formed with aninverter PCB of the power supply apparatus. Therefore, the sensed signalis independent of the output power, thereby increasing sensingefficiency.

Although the exemplary embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these exemplary embodiments but various changes andmodifications can be made by one ordinary skilled in the art within thescope of the present invention as hereinafter claimed.

1. A power supply apparatus comprising: an inverter controlleroutputting an externally provided direct current in response to apredetermined control signal; a power transforming part converting thedirect current into an alternating current, and transforming voltage ofthe alternating current to output a first polarity current and a secondpolarity current; and a connecting part outputting the first polaritycurrent to a first end portion of a load through a first terminal, theconnecting part outputting the second polarity current to a second endportion of the load through a second terminal, and the connecting parthaving a third terminal to receive a sensed signal in response to thefirst or second polarity currents so as to output the sensed signal,wherein the first terminal is spaced apart from the second terminal by afirst insulating distance, and the third terminal is spaced apart fromthe first or second terminals adjacent to the third terminal by a secondinsulating distance.
 2. The apparatus of claim 1, further comprising apower sensor disposed adjacent to the first or second end portions ofthe load so as to sense a level of the alternating current applied tothe load.
 3. The apparatus of claim 1, further comprising a detectingsignal generating part comparing the sensed signal output from the thirdterminal with a predetermined reference signal to generate the controlsignal, thereby providing the control signal to the inverter controller.4. The apparatus of claim 1, wherein the first and second insulatingdistances are no less than 3 mm and 2 mm, respectively.
 5. The apparatusof claim 1, wherein the inverter controller, the power transforming partand the connecting part are formed on one substrate.
 6. A backlightassembly comprising: a lamp driving part converting an externallyprovided direct current into an alternating current, and transformingvoltage of the alternating current to output the alternating current; alight emitting part including a lamp having a first end portion to whichhigh voltage alternating current is applied, and generating a light inresponse to the transformed alternating current; and a light controllerincreasing luminance of the light, wherein the lamp driving partincludes: an inverter controller outputting the externally provideddirect current in response to a predetermined control signal; a powertransforming part converting the direct current into the alternatingcurrent, and transforming voltage of the alternating current to output afirst polarity current and a second polarity current; and a connectingpart outputting the first polarity current to a first end portion of aload through a first terminal, the connecting part outputting the secondpolarity current to a second end portion of the load through a secondterminal, and the connecting part having a third terminal to receive asensed signal in response to the first or second polarity currents so asto output the sensed signal, wherein the first terminal is spaced apartfrom the second terminal by a first insulating distance, and the thirdterminal is spaced apart from the first or second terminals adjacent tothe third terminal by a second insulating distance.
 7. The backlightassembly of claim 6, further comprising a power sensor disposed adjacentto the first or second end portions of the lamp so as to sense a levelof the alternating current applied to the lamp.
 8. The backlightassembly of claim 7, wherein the power sensor includes a coil.
 9. Thebacklight assembly of claim 7, wherein the lamp driving part furthercomprises a detecting signal generating part comparing a sensed signalfrom the power sensor with a predetermined reference signal to generatea detecting signal, the detecting signal generating part providing thedetecting signal to the inverter controller as a control signal so as toprovide a constant current to the lamp.
 10. The backlight assembly ofclaim 9, wherein the power transforming part further comprises atransformer having a first windings and a second windings so as totransform the voltage of the alternating current, and wherein the powersensor sensing a voltage in accordance with an electric field generatedin response to a current flowing through the second windings, andproviding the sensed voltage to the detecting signal generating part asa sensed signal.
 11. The backlight assembly of claim 9, wherein the lampdriving part includes a plurality of the detecting signal generatingparts and a plurality of the power sensors, and a number of thedetecting signal generating parts is no more than a number of the powersensors.
 12. The backlight assembly of claim 7, wherein the lampincludes an EEFL.
 13. The backlight assembly of claim 12, wherein thelamp driving part includes a plurality of the EEFLs, and the powersensor is connected to at least one of the EEFLs.
 14. The backlightassembly of claim 7, wherein the lamp includes a plurality of the EEFLsconnected to each other in parallel.
 15. The backlight assembly of claim7, wherein the power transforming part includes a transformer having afirst windings and a second windings so as to transform voltage of thealternating current, and the power sensor is disposed adjacent to thesecond windings of the transformer.
 16. The backlight assembly of claim6, wherein the power transforming part supplies a constant voltage, ofwhich positive-polarity and negative-polarity levels of the transformedalternating current are substantially equal to each other, to the lamp.17. The backlight assembly of claim 6, wherein the power output partsupplies a constant voltage, of which minimum and maximum levels of thetransformed alternating current are substantially equal to each other,to the lamp.
 18. The backlight assembly of claim 6, wherein the invertercontroller comprises: a controlling part generating a switching signalto control an output of a constant current applied to the lamp inresponse to an on/off signal and an externally provided dimming signal;a switching part turning on or turning off an output of the directcurrent in response to the switching signal; and an inverting partconverting the direct current supplied through the switching part into afirst alternating current to supply the first alternating current to thepower transforming part.
 19. The backlight assembly of claim 18, whereinthe inverter controller further comprises a diode having a cathodeconnected to an output terminal of the switching part and an anodegrounded so as to prevent a rush current output from the inverting partfrom being supplied to the switching part.
 20. The backlight assembly ofclaim 6, wherein the inverter controller further comprises a switchdriving part amplifying a signal used to control a level of thealternating current output from the controlling part, and supplying theamplified signal to the switching part.
 21. An LCD apparatus comprising:a backlight assembly including a lamp driving part converting anexternally provided direct current into an alternating current, andtransforming voltage of the alternating current to output thealternating current, a light emitting part including a lamp having anend portion, to which high voltage alternating current is applied, andgenerating light in response to the transformed alternating current, anda light controller increasing luminance of the light; and a display unitdisposed on the light controller to receive the light from the lightemitting part through the light controller, thereby displaying an image,and wherein the lamp driving part includes an inverter controlleroutputting the externally provided direct current in response to apredetermined control signal; a power transforming part converting thedirect current into the alternating current, and transforming a voltageof the alternating current to output a first polarity current and asecond polarity current; and a connecting part outputting the firstpolarity current to a first end portion of the lamp through a firstterminal, the connecting part outputting the second polarity current toa second end portion of the lamp through a second terminal, and theconnecting part having a third terminal to receive a sensed signal inresponse to the first or second polarity currents so as to output thesensed signal, and wherein the first terminal is spaced apart from thesecond terminal by a first insulating distance, and the third terminalis spaced apart from the first or second terminals adjacent to the thirdterminal by a second insulating distance.
 22. The LCD apparatus of claim21, wherein the first and second insulating distances are no less thanabout 3 mm and about 2 mm, respectively.
 23. The LCD apparatus of claim21, wherein the inverter controller, the power transforming part and theconnecting part are formed on one substrate.
 24. The LCD apparatus ofclaim 21, further comprising a power sensor disposed adjacent to thefirst or second end portions of the lamp so as to sense a level of thealternating current applied to the lamp.
 25. The LCD apparatus of claim21, further comprising a detecting signal generating part comparing thesensed signal output from the third terminal with a predeterminedreference signal to generate the control signal, thereby providing thecontrol signal to the inverter controller.